Some amps have 2 individual, separate channels while others aren completely separate. What gives?
Many older amps have 2 completely separate channels, one usually featuring reverb and tremolo and the other not. This was done when it was fairly common to use one amp for several instruments at a time. That is not considered a good idea nowadays. More recent amps feature two unique channels, usually one clean and one for distortion and the player switches from one to the other. On many of the lower priced amps the tone controls are shared and the player just switches in and out the distortion circuit.